So far, as a method of refining and recovering a hydrogen gas from a hydrogen-containing gas, there are methods such as a method in which impurities are separated and removed by use of a pressure swing absorption method (PSA method) that makes use of an absorbing agent and a method for separating hydrogen by use of an organic or inorganic hydrogen separating membrane. The method that uses a hydrogen separating membrane is gathering attention in view of energy saving, separation efficiency, simplicity of apparatus configuration, easiness in operation and so on.
As the hydrogen separating membrane, membranes of organic polymers such as polyimide, polysulfone and so on; porous membranes of inorganic materials such as porous glass, porous ceramics and so on; and membranes of palladium or palladium alloys can be cited. For instance, in JP-A-07-124453, steps of forming a hydrogen separating membrane are described, in which on one surface of a metal support thin films of palladium and other metal, respectively, are alternately deposited by means of electroplating, on one surface of the metal support a lot of fine holes are bored by means of etching, heat treatment is applied to form a palladium alloy, furthermore a surface of a metal plate is etched to form a lot of fine holes, and these are integrated to form a hydrogen separating membrane.
However, there are problems in that it is difficult to form a plating layer excellent in the adherence directly on a metal support plate such as a stainless steel sheet and so on as mentioned above; and an alloy layer of palladium and nickel in the lastly applied heat treatment step may not be stably formed with a definite thickness.
Furthermore, there is another problem in that since in the plating, defects such as pinholes and so on are likely to occur, thin films of metal such as palladium and so on are formed with pores. In particular, in the case of multi-layered plating being applied, since the conditions such as a plating bath composition, an electric current, a temperature and so on have to be strictly controlled; that is, it becomes a very cumbersome process.
Still furthermore, there is still another problem in that since an exposed area of a thin film of metal such as palladium and so on cannot be made larger, there is a limit in an amount of permeable gas.
An object of the present invention is to provide a gas separating unit in which, in separating hydrogen gas, an effective area of a material capable of separating a hydrogen gas can be made larger and a method for manufacturing the same.
Furthermore, another object of the invention is to provide a method for manufacturing a gas separating unit that takes the handlability of a material capable of separating a hydrogen gas into consideration.
Still furthermore, still another object of the invention is to provide a gas separating unit that can increase an exposed area of a material capable of separating a hydrogen gas and can increase an amount of permeable hydrogen gas.